This invention relates to a circuit for driving an ultrasonic scaling probe suitable for use in dentistry, primarily for removal of plaque, cements, composites, etc. The invention utilizes an automatically tuned drive circuit.
Electronic circuits have been employed for driving ultrasonic dental scalers. By way of example. Sharp (U.S. Pat. No. 5,451,161) discloses such a circuit operative with a scaler insert for a hand piece of a dental scaler unit. The circuitry produces an oscillation at a frequency established by the insert, and employs the energizer coil of the hand piece as a feedback coil for operation of the circuit. Different scaler inserts are operative at different frequencies and, accordingly, the circuitry includes a manual switching of capacitors to adjust oscillation frequency.
As a further example, German patent 3,136,028 also employs the energizer coil as a part of a feedback portion of an oscillator circuit. Multiple frequencies of oscillation are obtained by use of a variable resistor and capacitor as a part of the oscillator circuit. Also, Sharp (U.S. Pat. No. 5,730,594) discloses a switch which operatively switches between an automatic tuning and a manual tuning of an oscillator circuit for the driving of the dental scaler.
The foregoing circuits suffer from the disadvantage of requiring manual intervention in the operation of the drive circuit to establish a specific frequency of operation as may be required by the specific choice of a scaler insert for the hand piece. In addition, the foregoing circuits, while providing for the capacity of enabling different frequencies of operation, do not have a facility for automatically establishing a desired amplitude of drive signal for the scaler insert as a function of the operating frequency, or even maintaining a constant amplitude throughout an operating frequency range of the drive circuit.